Frank Dobson's campaign to become Labour's candidate for London mayor has run into fresh problems over accusations that it is receiving unfair help from the party hierarchy.

Mr Dobson's two rivals for the Labour nomination, Ken Livingstone and Glenda Jackson, have responded angrily to the claims, with Mr Livingstone calling for the party's general secretary to resign - if she had acted improperly.

According to the BBC's Panorama programme, Labour general secretary Margaret McDonagh helped facilitate the release to the Dobson camp of a full address list of Labour London members.

The lists have been used by the Dobson campaign to send out mail shots to all Labour's 62,000 London members, who will vote in the new year for one of the three candidates.

Party rules require officials to remain neutral in internal elections.

In a statement to Panorama, the general secretary said it was "wholly untrue" that she had any involvement in the supply of a membership list that reached the Dobson campaign.

Since MEPs had an "automotatic and constitutional right" to lists, her authority for their release would not anyway have been required.

Ms McDonagh said Panorama was seeking to "establish a conspiracy where none existed."

The accusations come as the battle to win the Labour nomination takes on fresh significance after the main Tory challenger for mayor, Steve Norris, was dumped out of the race by a Tory party selection committee at the weekend.

According to Panorama, Linda Smith, the political assistant of London MEP Claude Moraes, approached Millbank for the lists as soon Mr Dobson announced he was standing.

She was initially refused, but the programme alleges the general secretary was then contacted by another Labour Party official and asked if she could help.

The request was prioritised and within about 24 hours computer discs with the names and addresses of all Labour members were biked to Ms Smith, who passed them on to the Dobson campaign.

Ms Jackson told the programme that if the allegations were true, it is "offensive beyond words that people would be cheated in that way".

Mr Livingstone said: "If it can be shown that the general secretary orchestrated the passing of these lists, in any fair world the general secretary should resign.

"Only I should imagine what they will do is give her a pay increase, given the present state of affairs."

Responding to the charges a Labour Party spokesman said: "We do not take the Panorama allegations seriously.

"Panorama came to us with a long shopping list of allegations based on anonymous sources. They received a full rebuttal of these allegations, both in general and in particular.

"They have constructed an elaborate conspiracy theory by wilfully ignoring or misrepresenting the information they were given."

Mr Dobson told Panorama: "The point I have made all along is that I got my people to ask at the beginning for us to be given the list officially on the assumption that such a list would go to all candidates."

When similar allegations surfaced earlier in the campaign the other two candidates complained that even if they were given a full list of party members they would not have had sufficient funds to pay for a mail shot in any case.